Samuel maxwell west croskery



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S. M. W; G-ROSKERY. ATTACHMENT FOR SEXTANTS.

No. 544,212. Patented Aug. 6,1895.

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ATTACHMENT FOR SEXTANTS. No. 544,212. Patented Aug. 6, 1895.

JamueZMaxu/efl W262 Graak e 71 UNITED STATES PATENT OFFICE.

SAMUEL MAXWELL WEST OROSKERY, OF ROCKFERRY, ENGLAND.

ATTACH M ENT FOR SEXTANTS.

SPECIFICATION forming part of Letters Patent No. 544,212, dated August6, 1895.

Application filed April 12 1895.

To all. whom it may concern:

Be it known that I, SAMUEL MAXWELL WEST ORosKERY, a subject of the Queen'of Great Britain, residing at Rockferry, in the county of Chester,England, have invented certain new and useful Improvements inAttachments for Sextants; and I do hereby declare the following to be afull, clear,and exact description of the invention, which will enableothers skilled in the art to which it appertains to make and use thesame.

My invention relates to various new and useful improvements in sextants,and more particularly to an improved manner of mounting the instrumentfor use in heavy weather, and further toa novel construction ofartificial horizon which can be quickly attached to and removed from thesextant.

The objects of the invention are to provide an improved form of supportto which an ordinary sextant may be applied for sustainv ingtheinstrument in heavy weather, when the vessel is rolling or pitching tooseverely to allow the-instrument to be properly used when held by handin the usual way, and to provide and producean improved construction ofartificial horizon which can be easily applied to any form of sextantand which will be simple in construction and absolutely accurate inoperation, both in the day-time and at night.

An artificial horizon is of especial advantage for use with sextantswhen the natural horizon is obscured and the sun or stars are visible,as is frequently the case in the North Atlantic ocean, where low densefogs are prevalent during the summer months.

In order that my invention may be understood, attention is directed tothe accompanying drawings, forming a part of this specifi cation, inwhich- Figure 1 is a sectional view of the entire device; Fig. 2, anenlarged front elevation of a well-known form of sextant, showing myimproved artificial horizon applied thereto; Fig. 3, an enlargedcross-sectional view of a, portion of the sextant-support, showing thesextant applied thereto; Fig. 4, an enlarged side elevation, partly insection, ofthe improved artificial horizon; Fig. 5, a cross-sectionalview on the line a: a: of Fig. 4; Fig. 6, an enlarged view of thehorizon-glass, show- Serial No. 545,495. (No model.)

ing the two sights and illustrating its appearance when a star has beenbrought down to the horizon. Fig. 7 is an enlarged detached view of oneof the'sights, and Fig. 8

is a perspective view of the screen to be used with the device atnight.

In all of the above views corresponding parts are designated by the sameletters of reference.

A represents a suitable casing, made preferably four or five feetinheight, and of wood or metal. This casing is preferably carried on thebridge or some other exposed place of the vessel. I

B B are two rings one within the other, and supported on suitableknife-edge bearings C, so as to form ordinary gimbals, such as are usedfor supporting compasses. Secured to the inner ring B and extending downwithin the casing A is a vessel D of any suit able depth.

E is a gimbal-ring mounted within the inner ringB on knife-edgebearing-pieces F, and mounted within this gimbal-ring E, on similarbearing'pieces, is a disk G. This disk G is provided with adependingintegral sleeve H, having a screw-threaded opening therein forreceiving a rod I, which carries a weight J at its lower end, whichweight J, as will be understood, will be suspended within the vessel D.Glycerin, oil, or any other viscid liquid is supplied to the vessel D,so as to immerse the weight J, to prevent violent movement of the latterwhen the vessel rolls or pitches. 1

-The disk G is provided on its upper side with a shoulder K, to which ametal diskLof larger diameter than the disk G is secured other way. Thedisk L is provided at its center with a bearing-pin N, made preferablyconical, and mounted on this bearing-pin is a tableO, preferably ofabout the same diameter as the top of the casing A, and'which may beconveniently made of wood. This table 0, being mounted on the pin N, isfreeto turn upon the disk L, and if desired, any approved form ofhearing, such as balls/or rollers, may be interposed between the movingparts.

A'set screw P engaging the bearing pin N may be employed to prevent-thetable Ofrom becoming accidentallyunseated. Q is a vertical standardextending up from the table 0 at one side of the bearing pin N, andprovided with an integral support or base R. This base R is providedwith slotted openings S therein, through each of which extends a screwT, engaging in the table 0. By making the openings for these screwsslotted, as shown, the position of the standard Q with respect to thecenter of the table may be adjusted so as to balance sextants ofdifferent weights.

The sextant, which will be presently de scribed, is adapted to beremovably secured to the standard Q, by means of thumb-screws U, or inany other suitable way. Such a support for the sextant as I have abovedescribed is particularly adapted for use during very rough weather whenthe vessel is pitching or rolling heavily, although it may be employedfor supporting the sextant at all times. It will be observed that thetable 0, which carries the sextant, may be turned on the pin N, so as tobe pointed toward the sun or star from which the observation is to betaken, and that said support is mounted practically in two sets ofgimbals, each setbeing entirely independent of the other. By mountingthe vessel D, which carries oil at its lower end, in gimbals B B, saidreceiving-vessel will always be kept practically vertical, and bymounting the table 0 in other gimbals E and G the sextant at all timeswill be entirely uninfiuenced by movements of the vessel, the steadinessthereof being very materially increased byimmersing the weight J in oil,as explained.

Referring to Figs. 2, 3, 4, 5, 6, and 7 the construction of my improvedartificial horizon and manner of applying the same to a sextant will bereadily understood.

a represents the plane or body of an ordinary form of sextant.

b is the silvered index-glass, which is usually provided with screws forits adjustment.

0 are the fore shades or screens of colored glass.

d is the horizon-glass, supported in a frame in the usual way, one sideof which is silvered as shown in Fig. 6.

e are the back shades or screens of colored glass, which are used toprevent the eyes from being injured by the glare of the sun.

fis the radius, which carries the index-glass Z) at its upper end andwhich works along the scale g. The radius f is generally provided at itslower end with a Vernier to enable accurate adjustments to be taken. Ahandle h is secured to the back of the plane a, and is attached bymeansof the set-screws U to the standard Q when itis desired to support thesextant, as explained.

iis the telescope, which is useful for ob taining accurate results onthe natural horizon, but which is not necessary when my improvedartificial horizon is used, an ordinary tube being suitable for thispurpose.

Referring to Figs. 4 and 5, j represents a small metallic vessel madepreferably of the general form shown. 7.: is a short bracketarm formed011 the back of the vessel 7', and having a slot Z therein. m is aset-screw engaging with the frame of the sextant and passing throughthis slot Z, whereby the position of the vessel j can be quickly andeasily adjusted.

n is a small shaft having very fine bearings formed in the front andback of the vessel If desired, the ends of this shaft 07. may be workedin jewels to prevent wear.

0 is a curved arm carried on the shaft n, and with its free ends aboutin line with the center of the horizon-glass (1. One end of this arm 0is in front of the horizon-glass and the other end is behind thehorizon-glass, as will be seen. Instead of making use of the curved arm0 it isobvious that a straight horizontal arm having vertical extensionsat each end may be employed.

p is a heavy weight depending from the shaft n and working within thevessel j. Glycerin or oil is poured in the vessel j, as shown, so as toimmerse the lower end of the weight 19. A notch q is formed in thebottom of the weight 19, so as to afford a greater resistance to theweightin its movement through the liquid in the vessel. A partition 7'is provided at the upper part of the vessel, directly beneath the shaftn, so that when the sextant is laid on its side the liquid in the vesselj will not escape.

s is a set-screw working in the front piece of the vessel j for engagingwith the weight 2) or with the shank which supports the weight 19 whenthe device is not in use, to prevent the weight from swingingunnecessarily.

Each end of the curved arm 0 is provided with a slot t therein, andengaging in each of said slots is a sight u. Each sight u is providedwith a shoulder v, with a screw-threaded portion w, with which athumb-nut :10 engages, and the point of the sight is coated withphosphorus luminous paint, which appears, as on the drawings, like ahead or ball, or is illuminated in any other way.

The sight u adjacent to the telescope t is shorter than the other sight,whereby the two heads 3/ y will appear to be side by side, as shown inFig. 6.

lVhen the device is to be used at night it is desirable to employ ascreen 2, covered with lampblack or otherwise suitably blackened, sothat the luminous heads y y will be sharply defined. This screen 2 isremovably secured, preferably, to the front side of the vessel 3 bymeansof a supporting-arm or, held in place by a set-screw b. The end ofthe arm a. opposite to the screen .2 is provided with a pin 0, whichengages in a. recess in the front of the vessel j and which serves tosteady the arm a.

The operation of my improved artificial horizon is as follows: Thedevice must be first adjusted to the natural horizon, which isaccomplished by supporting the device in as rigid a position aspossible, preferably by too TIC

,ineans of the support shown in Fig. 1, and by so adjusting the sights uin the slots tthat both of said sights will be in line with the horizon.-When this is done the device needs no further adjustment or attention,because the weight p will always keep the sights 'y y in line with thehorizon, and when the natural horizon is-obscured the operator iscertain that these sights y y indicate with absolute accuracy thenatural horizon. The sextant is therefore held in such a position thatthe heads y y will appear to be side by side, as shown in Fig. 6, andthe sun is brought down on the silvered portion of the horizonglassuntil the lower end of its reflected image is in line with the sights yy.

When the device is to be used at night for taking the altitude of afixed star the screen 2 is employed, so that the illuminated heads orsights y y will be sharply defined and will be side by side. The star isthen brought down in the same way until it is defined on the silveredportion of the horizon-glass in line with the heads y y. I find that inactual practice by coating the heads 1 y with phosphorus they aredefined very sharply, so that when a fixed star is brought down in linewith them the appearance of three stars side by side is produced.

It is of course obvious that my improved artificial horizon may beapplied to quadrants or to other instruments wherein the position of thenatural horizon must be found.

Having now described my invention, what I claim as new, and desire tosecure by Letters Patent, is as follows:

1. The combination of a casing A, a vessel D mounted in gimbals at thetop of said casing; a disk G mounted in gimbals at the top of saidvessel; a weight J carried by said disk and immersed in a liquid withinsaid vessel; a bearing spindle N at the top of said disk G; a revolvingtableO mounted on said bearing spindle; and a sextant carried by saidrevolving table, substantially as set forth.

2. The combination of a casing A, a vessel D mounted in gimbals at thetop of-said casing; a disk G mounted in gimbals at the top of saidvessel; a weight .T carried by said disk G and immersed in a liquidwithin said vessel; a bearing spindle N carried by said disk G; arevolving table 0 mounted on said bearing spindle N; a standard Qadjustably mounted on said table 0; and a sextant removably secured tosaid standard Q, substantially as set forth.

3. The combination with a sextant, of an artificial horizon removablyattached thereto, comprising two sights supported in a horizontal plane,said sights being of different lengths and having enlarged outer ends orheads, whereby said enlarged outer ends or heads will appear side byside when in operation, substantially as set forth.

4:. The combination with a sextant, of an artificial horizon attachedthereto, comprising two sights supported in a horizontal plane, one oneach side of the horizon glass of the sextant, said sights being ofdifferent lengths and having enlarged outer ends or heads, whereby saidenlarged outer ends or heads will appear side by side when in operation,substantially as set forth.

5. The combination with a sextant of a removable artificial horizonattached thereto, and comprising two luminous sights in a horizontalplane; and a blackened screen supported behind said luminous sights,substantially as set forth.

6. The combination with a sextant of a removable artificial horizonattached thereto, comprising two luminous sights in a hori zontal plane,and a removable blackened screen behind said sights, substantially asset forth V 7. The combination with a sextant of a removable artificialhorizon attached thereto, comprising a vessel j; a curved arm 0 pivotedat the top of said vessel; a sight adjustably secured to each end ofsaid curved arm; a

weight 19 within said vessel for keeping said sights in a horizontalplane; a recess q in said weight; a liquid in said vessel in which theweight p is partly immersed; and a partition r at the top of saidvessel, substantially as set forth. a

This specification signed and witnessed the 3d day of April, 1895.

SAMUEL MAXWELL WEST CROSKERY. Witnesses: I

JOHN THORPE, Ms. S. THORNTON.

